Plotting

Most interaction with Gadfly is through the plot function. Plots are described by binding data to aesthetics, and specifying a number of elements including Scales, Coordinates, Guides, and Geometries. Aesthetics are a set of special named variables that are mapped to a geometry. How this mapping occurs is defined by the elements.

This "grammar of graphics" approach tries to avoid arcane incantations and special cases, instead approaching the problem as if one were drawing a wiring diagram: data is connected to aesthetics, which act as input leads, and elements, each self-contained with well-defined inputs and outputs, are connected and combined to produce the desired result.

Functions and Expressions

Along with the standard plot methods operating on DataFrames and Arrays described in the Tutorial, Gadfly has some special signatures to make plotting functions and expressions more convenient.

plot(f::Function, lower, upper, elements...; mapping...)
plot(fs::Vector{T}, lower, upper, elements...; mapping...) where T <: Base.Callable
plot(f::Function, xmin, xmax, ymin, ymax, elements...; mapping...)
spy(M::AbstractMatrix, elements...; mapping...) -> Plot

For example:

p1 = plot([sin,cos], 0, 2pi)
p2 = plot((x,y)->sin(x)+cos(y), 0, 2pi, 0, 2pi)
p3 = spy(ones(33)*sin.(0:(pi/16):2pi)' + cos.(0:(pi/16):2pi)*ones(33)')
hstack(p1,p2,p3)
x -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -34 -32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 -50 0 50 100 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 -2 -1 1 0 2 Color h,j,k,l,arrows,drag to pan i,o,+,-,scroll,shift-drag to zoom r,dbl-click to reset c for coordinates ? for help ? -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -34 -32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 -50 0 50 100 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 y x -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 -10 0 10 20 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 -2 -1 1 0 2 f(x,y) h,j,k,l,arrows,drag to pan i,o,+,-,scroll,shift-drag to zoom r,dbl-click to reset c for coordinates ? for help ? -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 -10 0 10 20 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 y x -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 -10 0 10 20 -8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 f1 f2 Color h,j,k,l,arrows,drag to pan i,o,+,-,scroll,shift-drag to zoom r,dbl-click to reset c for coordinates ? for help ? -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -3.0 -2.9 -2.8 -2.7 -2.6 -2.5 -2.4 -2.3 -2.2 -2.1 -2.0 -1.9 -1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 -4 -2 0 2 4 -3.0 -2.8 -2.6 -2.4 -2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 f(x)

Adding to a plot

Another feature is that a plot can be added to incrementally, using push!.

p = plot()
push!(p, layer(x=[2,4], y=[2,4], size=[1.4142], color=[colorant"gold"]))
push!(p, Coord.cartesian(fixed=true))
push!(p, Guide.title("My Awesome Plot"))
x -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 -6.0 -5.8 -5.6 -5.4 -5.2 -5.0 -4.8 -4.6 -4.4 -4.2 -4.0 -3.8 -3.6 -3.4 -3.2 -3.0 -2.8 -2.6 -2.4 -2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 9.2 9.4 9.6 9.8 10.0 10.2 10.4 10.6 10.8 11.0 11.2 11.4 11.6 11.8 12.0 -10 0 10 20 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 h,j,k,l,arrows,drag to pan i,o,+,-,scroll,shift-drag to zoom r,dbl-click to reset c for coordinates ? for help ? -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 -6.0 -5.8 -5.6 -5.4 -5.2 -5.0 -4.8 -4.6 -4.4 -4.2 -4.0 -3.8 -3.6 -3.4 -3.2 -3.0 -2.8 -2.6 -2.4 -2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 9.2 9.4 9.6 9.8 10.0 10.2 10.4 10.6 10.8 11.0 11.2 11.4 11.6 11.8 12.0 -10 0 10 20 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 y My Awesome Plot

Wide-formatted data

Gadfly is designed to plot data in so-called "long form", in which data that is of the same type, or measuring the same quantity, are stored in a single column, and any factors or groups are specified by additional columns. This is how data is typically stored in a database.

Sometimes data tables are organized by grouping values of the same type into multiple columns, with a column name used to distinguish the grouping. We refer to this as "wide form" data.

To illustrate the difference consider some historical London birth rate data.

births = RDatasets.dataset("HistData", "Arbuthnot")[:,[:Year, :Males, :Females]]
RowYearMalesFemales
1162952184683
2163048584457
3163144224102
4163249944590
5163351584839
6163450354820
............

This table is wide form because "Males" and "Females" are two columns both measuring number of births. Wide form data can always be transformed to long form (e.g. with the stack function in DataFrames) but this can be inconvenient, especially if the data is not already in a DataFrame.

stack(births, [:Males, :Females])
RowvariablevalueYear
1Males52181629
2Males48581630
3Males44221631
............
162Females76231708
163Females73801709
164Females72881710

The resulting table is long form with number of births in one column, here with the default name given by stack: "value". Data in this form can be plotted very conveniently with Gadfly.

plot(stack(births, [:Males, :Females]), x=:Year, y=:value, color=:variable,
     Geom.line)
Year 1500 1525 1550 1575 1600 1625 1650 1675 1700 1725 1750 1775 1800 1825 1850 1525 1530 1535 1540 1545 1550 1555 1560 1565 1570 1575 1580 1585 1590 1595 1600 1605 1610 1615 1620 1625 1630 1635 1640 1645 1650 1655 1660 1665 1670 1675 1680 1685 1690 1695 1700 1705 1710 1715 1720 1725 1730 1735 1740 1745 1750 1755 1760 1765 1770 1775 1780 1785 1790 1795 1800 1805 1810 1815 1820 1825 1500 1600 1700 1800 1900 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 1740 1750 1760 1770 1780 1790 1800 1810 1820 1830 Males Females variable h,j,k,l,arrows,drag to pan i,o,+,-,scroll,shift-drag to zoom r,dbl-click to reset c for coordinates ? for help ? -1.5×10⁴ -1.0×10⁴ -5.0×10³ 0 5.0×10³ 1.0×10⁴ 1.5×10⁴ 2.0×10⁴ 2.5×10⁴ -1.00×10⁴ -9.50×10³ -9.00×10³ -8.50×10³ -8.00×10³ -7.50×10³ -7.00×10³ -6.50×10³ -6.00×10³ -5.50×10³ -5.00×10³ -4.50×10³ -4.00×10³ -3.50×10³ -3.00×10³ -2.50×10³ -2.00×10³ -1.50×10³ -1.00×10³ -5.00×10² 0 5.00×10² 1.00×10³ 1.50×10³ 2.00×10³ 2.50×10³ 3.00×10³ 3.50×10³ 4.00×10³ 4.50×10³ 5.00×10³ 5.50×10³ 6.00×10³ 6.50×10³ 7.00×10³ 7.50×10³ 8.00×10³ 8.50×10³ 9.00×10³ 9.50×10³ 1.00×10⁴ 1.05×10⁴ 1.10×10⁴ 1.15×10⁴ 1.20×10⁴ 1.25×10⁴ 1.30×10⁴ 1.35×10⁴ 1.40×10⁴ 1.45×10⁴ 1.50×10⁴ 1.55×10⁴ 1.60×10⁴ 1.65×10⁴ 1.70×10⁴ 1.75×10⁴ 1.80×10⁴ 1.85×10⁴ 1.90×10⁴ 1.95×10⁴ 2.00×10⁴ -1×10⁴ 0 1×10⁴ 2×10⁴ -1.0×10⁴ -9.0×10³ -8.0×10³ -7.0×10³ -6.0×10³ -5.0×10³ -4.0×10³ -3.0×10³ -2.0×10³ -1.0×10³ 0 1.0×10³ 2.0×10³ 3.0×10³ 4.0×10³ 5.0×10³ 6.0×10³ 7.0×10³ 8.0×10³ 9.0×10³ 1.0×10⁴ 1.1×10⁴ 1.2×10⁴ 1.3×10⁴ 1.4×10⁴ 1.5×10⁴ 1.6×10⁴ 1.7×10⁴ 1.8×10⁴ 1.9×10⁴ 2.0×10⁴ value